The loss or failure of an organ or tissue is one of the most devastating and costly problems in human health care. In the United States alone, as many as twenty million patients per year suffer from various organ and tissue related maladies caused by burns, skin ulcers, diabetes, and connective tissue defects, such as bone and cartilage damage. More than eight million surgical procedures are performed annually to treat these cases, Further, over 70,000 people are on transplant waiting lists, and an additional 100,000 patients die each year due to the lack of appropriate organs (The Organ and Transplantation Network, 2004; http://www.ustransplant.org). The financial cost to care for these patients has been estimated to be as much as $400 billion annually (Langer, 1993, Science 26: 920-6). Tissue engineering, which integrates a variety of science and engineering disciplines to create functional tissues and organs for transplantation, has been evolving into one of the most promising therapies in regenerative medicine (Patrick, C. W. Jr, Mikos, A. G., McIntire, L. V., 1998, “Frontiers in Tissue Engineering”, Elsevier Science Ltd.).
Physicians and researchers study in vivo tissue composition and cellular orientation to characterize critical mechanisms of tissue and organ systems (Gabbay, et al., 2006, Annals of Plastic Surgery, 57(1):89-93; Alini, et al., 2008, European Spine Journal, 17(1): 2-19). This body of knowledge assists in defining healthy tissue, such that a template can be formulated to conceptually design replacement tissue from basic biological building blocks using in vitro manufacturing (Boland, et al., 2003, The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology, 272A(2):497-502; Griffith, et al., 2002, Science, 295:1009-1014; Zhou, et al., 2007, Virtual and Physical Prototyping, 2(4):217-223). Biomodeling is the engineered combination of physical components into a specific spatial construction in a flexible digital workspace. The goal of biomodeling is to leverage geometric positioning and proximity of specific biologics to bring functional abilities to cell aggregates (Murray, et al., 2007, J Endod, 33(4):377-90; Ciocca, et al., 2009, Comput Med Imaging Graph, 33(1):58-62; Barron, et al., 2004, Biomed Microdevices 6(2):139-47). Model parameters are subject to engineered manipulation and refinement. Using this control, best estimates of biological tissue can be generated.
The field of tissue engineering continues to make significant advances towards its ultimate goal of engineering a fully functional organ. For example, scaffold guided tissue engineering may now include the fabrication of extra-cellular matrices (ECM) that have the capabilities to maintain cell growth, cell attachment, and the ability to form new tissues. Three dimensional scaffolds often address multiple mechanical, biological and geometrical design constraints. Additionally, Computer Aided Tissue Engineering (CATE) has seen significant development in solid freeform fabrication (SFF) processes, including the fabrication of tissue scaffolds with precision control. For example, Precision Extrusion Deposition (PED) devices use computer aided motion and extrusion to precisely fabricate the internal and external architecture, porosity, pore size, and interconnectivity within the scaffold. The high printing resolution, precision, and controllability of the PED allows for closer mimicry of tissues and organs.
However, the demands of these technological advances also demand advances in the systems and equipment that support and enable the evolution of tissue engineering. For example, some cells prefer scaffolds built from stiff material, and stiff materials typically have a high melting point. While desirable, these biopolymers with high melting points have proven to be difficult to manipulate in the fabrication of 3D scaffolds. Thus, there is a need in the art for a device and system that allows for the extrusion of higher melting point materials in the fabrication of 3D scaffolds. The present invention satisfies this need.